With the discovery of a light Higgs boson () by the ATLAS and CMS Collaborations in 2012 [1]}, [2]}, [3]}, the standard model (SM) is complete as a low-energy effective theory describing all known fundamental particles and their interactions. However, several questions still remain with the theory, for example, why the mass of the observed Higgs boson is 125, whereas quantum loop corrections would be expected to drive the mass up towards the Planck scale. Many models of new physics beyond the SM predict additional particles that can affect the quantum corrections to the Higgs boson mass and resolve this so-called “hierarchy problem”. New states proposed include new particles such as supersymmetric partners of SM particles, or fourth-generation quarks.
